diff --git a/src/libcore/arc.rs b/src/libcore/arc.rs
index eb11c8f1c540..a6baae0d082b 100644
--- a/src/libcore/arc.rs
+++ b/src/libcore/arc.rs
@@ -206,6 +206,7 @@ mod tests {
     }
 
     #[test]
+    #[ignore] // this can probably infinite loop too.
     fn exclusive_arc() {
         let mut futures = [];
 
diff --git a/src/libcore/sys.rs b/src/libcore/sys.rs
index af93009874f0..1e4e5b17bb95 100644
--- a/src/libcore/sys.rs
+++ b/src/libcore/sys.rs
@@ -173,6 +173,7 @@ mod tests {
     }
 
     #[test]
+    #[ignore] // this can go into infinite loops
     fn condition_variable() {
         let lock = arc::arc(create_lock());
         let lock2 = arc::clone(&lock);